1. Field of the Invention
This invention relates to a pulverulent borosilicate composition and a method of making a cellular borosilicate body and, more particularly, to a pulverulent borosilicate composition and a cellular body formed without employing conventional glass-making techniques, such as mixing and melting.
2. Description of the Prior Art
In prior art glass-making technology, it is known to produce borosilicate glasses by the conventional glass-making techniques of mixing and melting. It is also known to produce borosilicate powders by reacting intimate mixtures of silica and boric oxide with or without other oxides at elevated temperatures below the melting point of any of the constituent oxide materials to produce borosilicate powders having certain desired properties. Moreover, it is known, whether produced from an initial melt or as a reaction product from an intimate mixture, borosilicate glasses may be reduced to a fine powder, mixed with a cellulating agent or agents and cellulated to produce a borosilicate cellular glass product.
U.S. Pat. No. 3,762,936 discloses borosilicate glass powder formed directly from an admixture of boric oxide and amorphous silica. U.S. Pat. No. 3,354,024 discloses a process for making cellular glass from a borosilicate glass cullet and a cellulating agent. U.S. Pat. No. 3,793,039 discloses an alumino borosilicate cellular glass body formed from an admixture of clay, anhydrous boric oxide and potassium hydroxide without subjecting the admixture to the conventional melting techniques.
None of the known cellular products produced by the prior art processes have been found capable of providing the following durability criteria: (1) resist degradation by an electrolytic salt bath and corrosive gases at elevated temperatures, (2) resist attack by liquid nonferrous metals and especially attack at an interface zone between an electrolytic salt bath and a liquid metal, and (3) retain physical integrity, especially insulation properties under a load of about 17 psi at 700.degree. C.
For certain industrial applications, one or more of the above criteria have been found desirable and indeed necessary. There is a need for a pulverulent borosilicate composition that may be cellulated to form a cellular body that has one or more or all of the foregoing criteria.